.\" $OpenBSD: DH_get0_pqg.3,v 1.5 2018/12/21 21:54:48 schwarze Exp $
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.Dd $Mdocdate: December 21 2018 $
.Dt DH_GET0_PQG 3
.Os
.Sh NAME
.Nm DH_get0_pqg ,
.Nm DH_set0_pqg ,
.Nm DH_get0_key ,
.Nm DH_set0_key ,
.Nm DH_clear_flags ,
.Nm DH_test_flags ,
.Nm DH_set_flags ,
.Nm DH_get0_engine ,
.Nm DH_set_length
.Nd get data from and set data in a DH object
.Sh SYNOPSIS
.In openssl/dh.h
.Ft void
.Fo DH_get0_pqg
.Fa "const DH *dh"
.Fa "const BIGNUM **p"
.Fa "const BIGNUM **q"
.Fa "const BIGNUM **g"
.Fc
.Ft int
.Fo DH_set0_pqg
.Fa "DH *dh"
.Fa "BIGNUM *p"
.Fa "BIGNUM *q"
.Fa "BIGNUM *g"
.Fc
.Ft void
.Fo DH_get0_key
.Fa "const DH *dh"
.Fa "const BIGNUM **pub_key"
.Fa "const BIGNUM **priv_key"
.Fc
.Ft int
.Fo DH_set0_key
.Fa "DH *dh"
.Fa "BIGNUM *pub_key"
.Fa "BIGNUM *priv_key"
.Fc
.Ft void
.Fo DH_clear_flags
.Fa "DH *dh"
.Fa "int flags"
.Fc
.Ft int
.Fo DH_test_flags
.Fa "const DH *dh"
.Fa "int flags"
.Fc
.Ft void
.Fo DH_set_flags
.Fa "DH *dh"
.Fa "int flags"
.Fc
.Ft ENGINE *
.Fo DH_get0_engine
.Fa "DH *d"
.Fc
.Ft int
.Fo DH_set_length
.Fa "DH *dh"
.Fa "long length"
.Fc
.Sh DESCRIPTION
A
.Vt DH
object contains the parameters
.Fa p ,
.Fa g ,
and optionally
.Fa q .
It also contains a public key
.Fa pub_key
and an optional private key
.Fa priv_key .
.Pp
The
.Fa p ,
.Fa q ,
and
.Fa g
parameters can be obtained by calling
.Fn DH_get0_pqg .
If the parameters have not yet been set, then
.Pf * Fa p ,
.Pf * Fa q ,
and
.Pf * Fa g
are set to
.Dv NULL .
Otherwise, they are set to pointers to the internal representations
of the values that should not be freed by the application.
Any of the out parameters
.Fa p ,
.Fa q ,
and
.Fa g
can be
.Dv NULL ,
in which case no value is returned for that parameter.
.Pp
The
.Fa p ,
.Fa q ,
and
.Fa g
values can be set by calling
.Fn DH_set0_pqg .
Calling this function transfers the memory management of the values to
.Fa dh ,
and therefore they should not be freed by the caller.
The
.Fa q
argument may be
.Dv NULL .
.Pp
The
.Fn DH_get0_key
function stores pointers to the internal representations
of the public key in
.Pf * Fa pub_key
and to the private key in
.Pf * Fa priv_key .
Either may be
.Dv NULL
if it has not yet been set.
If the private key has been set, then the public key must be.
Any of the out parameters
.Fa pub_key
and
.Fa priv_key
can be
.Dv NULL ,
in which case no value is returned for that parameter.
.Pp
The public and private key values can be set using
.Fn DH_set0_key .
Either parameter may be
.Dv NULL ,
which means the corresponding
.Vt DH
field is left untouched.
This function transfers the memory management of the key values to
.Fa dh ,
and therefore they should not be freed by the caller.
.Pp
Values retrieved with
.Fn DH_get0_pqg
and
.Fn DH_get0_key
are owned by the
.Vt DH
object and may therefore not be passed to
.Fn DH_set0_pqg
or
.Fn DH_set0_key .
If needed, duplicate the received values using
.Xr BN_dup 3
and pass the duplicates.
.Pp
.Fn DH_clear_flags
clears the specified
.Fa flags
in
.Fa dh .
.Fn DH_test_flags
tests the
.Fa flags
in
.Fa dh .
.Fn DH_set_flags
sets the
.Fa flags
in
.Fa dh ;
any flags already set remain set.
For all three functions, multiple flags can be passed in one call,
OR'ed together bitwise.
.Pp
.Fn DH_set_length
sets the optional length attribute of
.Fa dh ,
indicating the length of the secret exponent (private key) in bits.
If the length attribute is non-zero, it is used, otherwise it is ignored.
.Sh RETURN VALUES
.Fn DH_set0_pqg ,
.Fn DH_set0_key ,
and
.Fn DH_set_length
return 1 on success or 0 on failure.
.Pp
.Fn DH_test_flags
return those of the given
.Fa flags
currently set in
.Fa dh
or 0 if none of the given
.Fa flags
are set.
.Pp
.Fn DH_get0_engine
returns a pointer to the
.Vt ENGINE
used by the
.Vt DH
object
.Fa dh ,
or
.Dv NULL
if no engine was set for this object.
.Sh SEE ALSO
.Xr DH_generate_key 3 ,
.Xr DH_generate_parameters 3 ,
.Xr DH_new 3 ,
.Xr DH_size 3 ,
.Xr DHparams_print 3
.Sh HISTORY
These functions first appeared in OpenSSL 1.1.0
and have been available since
.Ox 6.3 .
